The objective of the proposed methodological research is to improve the validity of prevalence estimates concerning heroin use and other highly stigmatized behaviors. This goal is pursued through the development and trial of a new data collection/estimation technique which has been designed to reduce the problem of respondent denial in surveys of particularly sensitive behaviors. This new technique has been provisionally termed the "item count technique." The conventional wisdom for minimization of question threat has proved inadequate for the study of behaviors such as heroin use; indeed, the available evidence indicates that official figures on heroin use may underestimate true prevalence by substantial margins. Since 1965, a number of innovative approaches have been developed with the purpose of reducing the problem of respondent denial. These indirect survey-based estimation techniques allow a statistically unbiased estimate of a sensitive behavior without requiring the respondent to articulate a direct response to the sensitive question. The newest and most promising technique in this series is the item count technique devised by the Social Research Group. Experience with previously reported techniques (e.g., randomized response) has revealed a variety of problems encountered in the field--problems which may undermine the overall validity of resulting estimates. In contrast, the strikingly simple item count technique is capable of avoiding all serious field-application problems. The development and preliminary evaluation of the item count technique is proposed here in terms of the lifetime prevalence of heroin use. The proposed work includes (1) item development based on pretesting in both "normal" and high-drug-use residential areas, and (2) a relatively inexpensive test of the technique's performance in a large-scale survey application. Heroin prevalence estimates obtained via the new procedure will be compared with existing conventional and indirect estimates.